The end of June is often a Good News/Bad News time for Hydrangeas. On the one hand, many varieties of this summer flowering shrub have come into beautiful bloom. On the other hand, it’s the time of year when we might notice that our plants have problems. Here’s a list of a few common Hydrangea difficulties and what you can do about them.
- Black spots on hydrangea leaves. This is a leaf-spot fungus that develops in rainy periods or when hydrangeas are hit with frequent irrigation. It does not harm the plant although it can look pretty awful at times. The fungus does not spread to other plants. You can cut off the worst leaves and if your sprinkler system (or hand watering) is hitting the foliage frequently adjust it so that you’re watering deeply but less often.
- Few flowers or no flowers. Your hydrangea isn’t flowering? Here are some of the reasons why your plant might not be blooming well. 1. Too much shade: Hydrangeas need about 3 hours of sun in order to flower well. 2. Improper pruning: big leaf hydrangeas (the ones with blue or pink flowering, either mop-head or lacecap) form their flower buds in the previous summer. If the canes are cut down in the fall or the spring you’ll have fewer flowers. 3. Winter temperatures or an exposed location: the germ of the flower bud might get zapped by winter temperatures (below five degrees Fahrenheit) or cold winter/spring winds. 4. Too much nitrogen: sometimes lawn fertilizer gets repeatedly washed or spread onto neighboring hydrangeas and this can contribute to the growth of leaves at the expense of the flowers.
- Flowers turn brown quickly. If your Hydrangea flowers dry out they will turn brown. Similarly, if the plants are growing in full or afternoon sun they will fade rapidly. Be sure to keep your shrubs deeply watered during hot weather. A layer of mulch around the plants will help keep the soil moist. In some situations a soaker hose that is wound around the plants underneath the mulch is a big help for hydrating Hydrangeas. If plants are in hot afternoon sun consider moving them to a location where they get sun in the morning and shade all afternoon.
- Holes in the leaves. There are assorted small green “fruit worms” (larvae) that eat hydrangea leaves. If you see holes in the leaves look underneath the foliage for such larvae. Spray with Captain Jack’s Deadbug Brew (Spinosad) making sure to coat under the leaves as much as possible.
- Plants are too tall. This isn’t really a problem with the Hydrangea but with the placement of the plant. A Hydrangea’s growth is genetically determined; some varieties, such as Nikko Blue, grow 6’ tall and 8’ wide. Others stay shorter. If your plant is too tall for the location there is no way to make it smaller again because the plant will replace any growth you cut in one season…the plant you cut down in autumn or spring will be just as tall the following July. Transplant larger plants to a location where they can get big and replace them with a variety that stays shorter. Note: CityLine Hydrangeas and the Forever & Ever series stay shorter.
- My hydrangea flowers are white and I want to turn them blue. White flowering hydrangeas won’t change color. You can change most pink-flowering plants to blues or purples by acidifying the soil with sulfur or aluminum sulfate, and turn blue shades pink by repeatedly applying lime around your plants, but you can’t alter white flowers. Some white blooming hydrangeas (varieties of H. paniculata) will turn pinkish as they age and others (H. arborescens) will turn green.
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